gh-89152: Note truth testing exception in stdtypes.rst (#137640)

Co-authored-by: Peter Bierma <[email protected]>
Co-authored-by: Jelle Zijlstra <[email protected]>

Author: 3 people

Doc/library/stdtypes.rst

@@ -46,8 +46,10 @@ Any object can be tested for truth value, for use in an :keyword:`if` or
 By default, an object is considered true unless its class defines either a
 :meth:`~object.__bool__` method that returns ``False`` or a
 :meth:`~object.__len__` method that
-returns zero, when called with the object. [1]_  Here are most of the built-in
-objects considered false:
+returns zero, when called with the object. [1]_ If one of the methods raises an
+exception when called, the exception is propagated and the object does
+not have a truth value (for example, :data:`NotImplemented`).
+Here are most of the built-in objects considered false:
 
 .. index::
    single: None (Built-in object)